1. Technical Field
The present disclosure relates to a surgical access apparatus for permitting the introduction of a surgical instrument into a body cavity. In particular, the disclosure relates to a seal assembly for the access apparatus and being adapted to form a seal about a surgical instrument while centering the surgical instrument within the apparatus.
2. Background of Related Art
There are many different types of minimally invasive surgical procedures whereby a surgeon gains access to an internal surgical site through a small opening in the body. For example, a laparoscopic procedure involves the insertion of instruments through a small opening in a patient's abdomen. Also, an arthroscopic procedure allows a surgeon to examine the interior of a patient's joint through a small incision in the skin. A comprehensive term, used throughout the present disclosure to refer to this type of procedure, is endoscopic surgery.
Typically in an endoscopic surgery, a small incision is made in the skin and a cannula is inserted through the fascia into a body opening. A cannula is a narrow tube, typically 5 to 13 mm in diameter, which serves generally to hold the incision open and provide a conduit to the body cavity through which a surgeon may introduce and withdraw the various surgical instruments required by the desired procedures. An insufflation gas (most commonly carbon dioxide) may be introduced through the cannula into the body opening establishing a slight pressure. This practice inflates the body opening and provides a viewing space wherein a surgeon may insert a camera lens to monitor the procedure. The surgeon may then use the insufflated space to maneuver a variety of other instruments into position to manipulate the targeted tissue without contacting and damaging the surrounding tissue.
Of primary concern in these procedures is establishing a fluid tight seal across the cannula to maintain the integrity of the insufflated body cavity. To maintain the insufflation pressure and the corresponding working space, many types of seals have been introduced. One common difficulty with conventional seals is the inability of the seal to accommodate the entire range of instruments necessary to complete a surgical procedure. A single surgical procedure will often require many instruments having dissimilar diameters. To ensure that a fluid-tight connection with each of these instruments is achieved, a surgeon might need to select an instrument seal having an aperture sized slightly smaller than the smallest diameter instrument to be used. Because the instrument seal is elastomeric, it is possible the aperture will be able to expand sufficiently to accept the largest diameter instrument, but there will be some associated difficulty. There is a friction force associated with moving the instrument while it is in contact with the aperture of the instrument seal. This friction force is sometimes called an insertion or glide force, and it must be kept low enough such that manipulating the instrument is not awkward for the surgeon. Inserting a large diameter instrument into a small diameter aperture will likely cause insertion and glide forces which are too large to be appropriate for the endoscopic procedures which often involve delicate movements.
One simple solution to this problem is to provide an instrument seal which is removable during surgery. In this way, a surgeon could select the instrument seal sized most appropriately for each instrument and install the seal just before use. Although effective, this process can be time consuming and unnecessarily prolong the surgery. Some devices have been introduced to hasten this process such as a smaller diameter instrument seal that can be flipped into and out of position with a simple movement positioned proximally in relation to a conventional stationary large diameter instrument seal. This type of system is most effective for use with a limited number of instruments having diameters very close to one of the two instrument seal apertures, but, a surgeon may still encounter difficulty with insertion forces or maintaining a seal with intermediately sized instruments.
Besides the accommodation of instruments of varying diameter, another characteristic desirable in an instrument seal is the ability of the seal to provide radial support to an instrument. Adequate radial support will aid in stabilizing the instrument so a surgeon will not need to divert attention from the surgical procedure to hold the instrument steady. Radial support is often provided by the very same features in a seal which assist in centering the instrument since providing a robust radial support at all points around the diameter of an instrument will naturally tend to keep the instrument centered. A need exists for an instrument seal capable of centering an elongated object and having an aperture that is truly flexible and modifiable in use. The seal should be able to accommodate an entire range of variously sized instruments without requiring any awkward manipulations to be performed by a surgeon.